I'm using ES 1.7.2. I've found that if weight field is > 0x40000000 (MAX_INT/2) resulting suggest score (and consequently suggests order) is unpredictable.
May be there is an overflow somewhere in code.
Also i've played with source code tests (e.g. testThatWeightCanBeAString from org.elasticsearch.search.suggest.CompletionSuggestSearchTests). Some of them failed when i use large weight values.